The invention relates to a cover of the spinbox of a rotor spinning machine. It also relates to a mounting plate for the attachment of the cover.
A cover of this type is known from the rotor spinning machine RU 14 of Schubert & Salzer, Maschinenfabrik Aktiengesellschaft, Ingolstadt, Federal Republic of Germany. Such covers, which are called rotor covers for short in the jargon used by specialists in the field, constitute part of the wall of the spinbox in which the spinning rotor rotates. Since the spinbox must be subjected to negative pressure during the formation of yarn it is closed and is usually subjected to active suction. The spinbox must be opened for maintenance of the rotor, e.g. for mechanical cleaning of the rotor and sometimes also for pneumatic rotor cleaning. This also applies when the rotor is to be replaced. The spinbox is opened by opening the cover which constitutes the rotor box or spinbox wall across from the open side of the spinning rotor.
For this purpose the cover is attached to a mounting plate which, in turn, constitutes the cover of the rotor box and is attached to the machine frame, for example, so as to be capable of pivoting in relation to the rotor. Such a rotor box is shown in German Patent Publication No. DE-OS 28 11 960, for example. Among other things, FIG. 2 of this publication shows a cover bearing the reference number 36. For the sake of simplification the mounting plate was omitted in this drawing. In the state of the art it is installed on the side of the cover away from the spinning rotor and, in turn, attached to the cover which is cover 32 in the drawings of No. DE-OS 28 11 960. As can be seen in the drawings of No. DE-OS 28 11 960, the cover not only serves to cover the rotor box but in addition contains a channel to feed fibers into the rotor. Bores for the arrival of cleaning air into the rotor as well as a bore to draw the yarn produced in the rotor out of the rotor box are also contained in the cover.
In a manner not shown in the schematic representation in the publication, the cover has a threaded bore in its back away from the rotor for connection of compressed air for rotor cleaning and a bore into which a yarn draw-off pipe is inserted from the back. It is connected to the cover by a stud screw running at a right angle to the bore.
The known rotor cover consists of an aluminum pressure-cast element that must be machined after casting. Especially threads for compressed-air connection and for the attachment of the yarn draw-off pipe must be installed and this causes an additional machining outlay. The known rotor cover forms a component on the rotor spinning machine which must be replaced from time to time by the operator of the machine. When the machine is changed over to a different yarn which is produced with a rotor of different diameter, the rotor cover must be replaced. The disadvantage of the known cover is that it is difficult to install and to remove. Due to the fact that the compressed-air circuit is connected by means of threads, the compressed-air circuit must first be removed in order to replace the cover and must be re-connected to the new cover to be installed, requiring the use of tools. The yarn draw-off pipe is also removed from the machine together with the removal of the rotor cover since it is firmly connected to the cover. As a result it must be removed from the disassembled cover and replacement of the yarn draw-off pipe, which is a wear part of the rotor spinning machine, is not possible without disassembly the cover.
The known mounting plate to which the cover is attached is provided with a contact surface upon which the rotor cover bears, as well as a threaded bore to screw on the rotor cover. Near the cover's air connection and yarn draw-off pipe the mounting plate is provided with a recess so that when the fastening screw of the cover is loosened, it may be removed together with the air connection and the yarn draw-off pipe. Air connections and yarn draw-off pipes remain firmly connected to the cover and must be removed from it later. This is awkward because of the lack of space and is time consuming. The installation of a new cover is accordingly complicated.